Geir Horn

Dr. Geir Horn

Department of Informatics, University of Oslo, 0316 Oslo, Norway
orcid

Research Focus & Metrics

Academic Career Length

23Years (2004-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

View All Publications
1 December 2012 in Journal of Systems and Software
Verified
Journal Article
Closed access
SHS. Hallsteinsen
S. Hallsteinsen
KGK. Geihs
K. Geihs
Nearchos PaspallisNearchos Paspallis
Nearchos Paspallis
FEF. Eliassen
F. Eliassen
Geir HornGeir Horn
Geir Horn
George Angelos PapadopoulosGeorge Angelos Papadopoulos
George Angelos Papadopoulos

15 September 2008 in Software: Practice and Experience
Verified
Journal Article
Closed access
PDF file
KGK. Geihs
K. Geihs
PBP. Barone
P. Barone
FEF. Eliassen
F. Eliassen
JFJ. Floch
J. Floch
RFR. Fricke
R. Fricke
ESE. Stav
E. Stav

23 November 2018 in IEEE Access
Verified
Journal Article
Open access
ATAmir Taherkordi
Amir Taherkordi
FZFeroz Zahid
Feroz Zahid
Yiannis VerginadisYiannis Verginadis
Yiannis Verginadis
Geir HornGeir Horn
Geir Horn

30 October 2009 in IEEE Transactions on Systems, Man, and Cybernetics, Part B (Cybernetics)
Verified
Journal Article
Closed access
Geir HornGeir Horn
Geir Horn
BOB. John Oommen
B. John Oommen
This paper considers the NP-hard problem of object assignment with respect to multiple constraints: assigning a set of elements (or objects) into mutually exclusive classes (or groups), where the elements which are ldquosimilarrdquo to each other are hopefully located in the same class. The literature reports solutions in which the similarity constraint consists of a single index that is inappropriate for the type of multiconstraint problems considered here and where the constraints could simultaneously be contradictory. Such a scenario is illustrated with the static mapping problem, which consists of distributing the processes of a parallel application onto a set of computing nodes. This is a classical and yet very important problem within the areas of parallel computing, grid computing, and cloud computing. We have developed four learning-automata (LA)-based algorithms to solve this problem: First, a fixed-structure stochastic automata algorithm is presented, where the processes try to form pairs to go onto the same node. This algorithm solves the problem, although it requires some centralized coordination. As it is desirable to avoid centralized control, we subsequently present three different variable-structure stochastic automata (VSSA) algorithms, which have superior partitioning properties in certain settings, although they forfeit some of the scalability features of the fixed-structure algorithm. All three VSSA algorithms model the processes as automata having first the hosting nodes as possible actions; second, the processes as possible actions; and, third, attempting to estimate the process communication digraph prior to probabilistically mapping the processes. This paper, which, we believe, comprehensively reports the pioneering LA solutions to this problem, unequivocally demonstrates that LA can play an important role in solving complex combinatorial and integer optimization problems.

1 May 2018
Verified
Conference Paper
Closed access
Geir HornGeir Horn
Geir Horn
PSPawel Skrzypek
Pawel Skrzypek
Cross Cloud deployment of applications allows for many additional benefits, like using the best Cloud provider for a given application component, increasing the reliability owing to the diversification of Cloud providers, and providing additional elasticity and capacity. On the other side, in practical applications, it is currently very difficult to properly plan and optimise the architecture of the application for cross Cloud deployment. Different Cloud providers uses different types of infrastructure, making direct comparisons difficult. Additionally, the requirements of the application could change over time and according to the application's execution context, workload, users, and many other aspects. This paper presents the fundamentals of the MELODIC solution based on a high level model of the application and dynamic, Cloud provider agnostic optimised deployment and reconfiguration of the application.

3 April 2017
Verified
Conference Paper
Open access
PDF file
ATAmir Taherkordi
Amir Taherkordi
FEFrank Eliassen
Frank Eliassen
Geir HornGeir Horn
Geir Horn
The large-scale deployments of Internet of Things (IoT) systems have introduced several new challenges in terms of processing their data. The massive amount of IoT-generated data requires design solutions to speed up data processing, scale up with the data volume and improve data adaptability and extensibility. Beyond existing techniques for IoT data collection, filtering, and analytics, innovative service computing technologies are required for provisioning data-centric and scalable IoT services. This paper presents a service-oriented design model and framework for realizing scalable and efficient acquisition, processing and integration of data-centric IoT services. In this approach, data-centric IoT services are organized in a service integrating tree structure, adhering to the architecture of many large-scale IoT systems, including recent fog-based IoT computing models. A service node in the tree is called a Big Service and acts as an integrator, collecting data from lower level Big Services, processing them, and delivering the result to higher level IoT Big Services. The service tree thereby encapsulates required data processing functions in a hierarchical manner in order to achieve scalable and real-time data collection and processing. We have implemented the IoT Big Services framework leveraging a popular cloud-based service and data platform called Firebase, and evaluated its performance in terms of real-time requirements.